This invention relates to a balloon catheter for use in delivering a medical device such as a stent to a desired body location, such as in a blood vessel. More specifically, this invention relates to a stent mounting region on a balloon catheter which has multiple balloon elements while are separated by spaces. Contained within the spaces between the balloon elements are stent mounting bodies which extend radially and act to receive and secure a stent, in its pre-delivered crimped form, to the balloon catheter.
In balloon expansion of a stent it is important that the stent be accurately positioned over the body portion of a balloon. Failure to properly position the stent over the balloon may result in an unintended non-uniform expansion of the stent. Furthermore, improper positioning of the stent with respect to the balloon during inflation may result in improper final placement of the stent within the body vessel. Failure to keep the stent securely positioned during balloon expansion may cause the expanded stent to shift in position or drift within the vessel prior to the final seating of the expanded stent.
The present invention addresses the above problems by ensuring proper securement and positioning of the stent over the balloon throughout the expansion process by utilizing a segmented balloon or multiple balloon elements respectively interspaced with a stent mounting body or bodies.
It is well known in the stent delivery art that a stent delivery apparatus, such as a balloon catheter, should have as low a profile as possible. However, due to the design and construction of many stents, the delivery apparatus will often require that additional protective layers be added to the catheter in order to protect the expansion balloon from being damaged by the stent during inflation, as well as to protect the anatomy of the vessel from being hooked or torn by the stent as it is inserted into the body. As such, numerous delivery catheters have employed multiple layer balloons, and complex sheath arrangements all of which undesirably increase the diameter of the delivery catheter.
One such multiple layer balloon catheter for delivering a stent is U.S. Pat. No. 5,807,327 to Green et al (Green), incorporated herein by reference. Green discloses a stent delivery catheter having a balloon (126) with three layers. A first or inner layer (138) is a burst resistant layer which has a second layer (140) disposed exteriorly of the first layer (138). Because of problems associated with the high coefficient of friction of the second layer (140) a third layer (142) may be wholly or partially added to the second layer (140). Green uses an excessive number of balloon layers to ensure that the balloon is uniformly inflated. The multiple layers of Green and other similar multiple layer balloon catheters have a greater profile than is desirable.
U.S. Pat. No. 5,647,847 to Anderson et al (Anderson), which is incorporated herein by reference, discloses a sheath for holding a device in a desired position against a balloon catheter for delivery in the lumen of a patient. By adding a sheath such as that which is shown in Anderson, an additional layer is added to the balloon catheter thereby undesirably increasing the profile of the catheter.
The present invention provides a low profile catheter capable of properly expanding and seating a stent. The low profile balloon catheter of the present invention utilizes one or more stent mounting bodies to secure the stent to the catheter, the bodies being arranged so that the balloon has minimal contact with the potentially sharp edges of the stent. The stent mounting bodies of the present invention provide the feature of ensuring that the stent is accurately and securely positioned on the balloon catheter with respect to the balloon, thereby ensuring proper expansion and positioning of the stent during balloon inflation.